The present invention relates to techniques for reducing power consumption in a speculative decision feedback equalizer by powering up the speculative path that is going to take the next decision based on the previous decision, and holding other paths in a reset low or reduced power condition.
Decision feedback equalizers (DFEs) are typically used in the receivers of communication systems in order to equalize dispersion of the transmission channels. Speculation or loop-unrolling is a technique that implements all the possible weighted summations at the output of a finite impulse response (FIR) filter in the DFE feedback path in order to reduce the critical-path time of the DFE coefficients summation time. All the possible combinations of N post-cursors ISI terms are generated in a speculative decision feedback equalizer of order N so that a total of 2N combinations or speculations are generated. The correct decision is selected among the 2N speculations on the base of the last N decisions.
Due to hardware complexity that grows exponentially, speculation is typically implemented for the first tap, although speculation may be beneficial for additional taps in very high speed receivers running at tens of Gb/s. As the hardware complexity grows, the power consumption also grows.
Accordingly, a need arises for techniques by which the power consumption in a speculative decision feedback equalizer may be reduced.